1. Field of the Invention
The present invention relates to an envelope waveform generation apparatus suitable for an electronic musical instrument.
2. Description of the Prior Art
As a conventional envelope waveform generation apparatus for an electronic musical instrument, an apparatus for generating an envelope waveform consisting of a plurality of states, e.g., an attack state, a decay state, and the like is known (e.g., Japanese Patent Publication No. 63-39072).
However, in a conventional envelope waveform generation apparatus, when a tone is to be sustained or a release time is prolonged upon a key OFF event, if a key OFF event is detected at an instance when the level of an envelope waveform is increased in, e.g., an attack state, the envelope waveform is sustained or released from the increased level, and the high-level envelope waveform is undesirably sustained for a long period of time. If tone volume control of a tone is performed according to this envelope waveform, a performance tone becomes unnatural.
If a key OFF event is detected extremely early, i.e., before an envelope waveform sufficiently rises, the envelope waveform begins to decay before an attack feeling is provided.
Furthermore, decay characteristics of an envelope waveform after a key OFF event are not changed regardless of the way of playing the musical instrument, and performance tones become monotonous.